Francisella tularensis (Ft)) is a Gram-negative, facultative intra-cellular pathogen and the etiological agent of tularemia, a disease that can be fatal in humans. Ft can infect individuals at both mucosal and peripheral sites, with the former being the most lethal form of infection. Both humoral and cellular immunity play a role in protection against this organism. While there are only about 200 known Ft infections per year in the U.S., as few as one organism can be fatal, if inhaled. This has led to the obvious concern that Ft could be used as a bioterrorism agent, when dispersed as an aerosol in a populated area. Thus, Ft has been listed as a category A select agent, and there is strong interest in the development of an effective vaccine against Ft.
Furthermore, the development of needle-free, mucosal vaccines that do not require exogenous adjuvants is of significant interest to all areas of infectious disease including biodefense. Even though some infections can be treated successfully with antibiotics, under some circumstances, such as biodefense, vaccination is preferred over post-exposure therapy.
To date, the current gold standard for tularemia prophylaxis, infection with viable Live Vaccine Strain (LVS) Ft, provides only moderate protection in humans. Thus, a need exists for a vaccine that yields improved efficacy and a major effort is underway to develop a new generation of safe and effective vaccines against the disease.